Sitting with it
Some people find it helps to spend a few quiet minutes with whatever an experience left behind — not to force meaning out of it, just to let it be present without immediately doing anything about it.
There is no required method. For some this looks like meditation; for others it is a slow walk without headphones, or lying still for a while. In one survey of 608 people who had extended difficulties after psychedelic use, meditation and prayer was the individual strategy most often reported as helpful (27%). That is self-report, not a clinical trial — it tells you what people turned to, not what is proven to work.
If stillness makes things feel worse, that is useful information, not a failure. Try something else on this shelf, or nothing at all.